Controller for electric motors



P. H. ZIMMER.

CONTROLLER FOR ELECTRIC MOTORS.

APPLICATION FILED JAN 8,1919.

1 ,343 ,021 Patented June 8, 1920.

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H i s Trttor'n eg P. H. ZIMMER.

CONTROLLER FOR ELECTRIC MOTORS.

APPLICATION FILED JAN. 8,19I9.

Patented June 8, 1920.

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Inventor: awl H. zimmer,

His flttorneg.

UNITED STATES PAUL H. ZIMMEB, OF SCHENEGTADY, NEW YORK, ASSIGNOR TOGENERAL ELECTRIC PATENT OFFICE.

COMPANY, A CORPORATION OF NEW YORK.

' CONTROLLER ron nnncrnrc MOTORS.

Specification of Letters Patent.

Patented June 8, 1920.

Application filed January 8, 1919. Serial No. 270,170.

To all whom it may concern.

Be it known that I, PAUL H. ZIMMER, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements in Controllersfor Electric Motors, of which the following is a specification.

My invention relates to starting devices for electric motors and has forits object the provision of improved means whereby an electric motor maybe started and brought up to running speed in a reliable, simple andefficient manner.

My invention relates more specifically to starting devices in which aswitch is first closed to make a starting connection and subsequently asecond or running switch is closed and the first switch opened.

My invention is particularly applicable to the starting of alternating.current motors of the type which are connected to a source of lowvoltage for starting and then connected directly to the line voltage forrun-- ning. One method of accomplishing this I result automatically isto provide two switches, one of which is first closed under manualcontrol to make the starting con nection and then at the proper time asecond switch which makes the running connection is automatically closedand the first switch opened. I have disclosed my invention .inconnection with an arrangement of this general character althoughcertain-features thereof may have a more general application.

In carrying out my invention in one form I provide twoelectromagnetically actuated switches, one for making the startingconnection which I-have illustrated as a connection to a compensator oraauto-transformer for applying a reduced voltage to the motor while theother switch in closing connects the motor direct to the line. The twoswitches are so interlocked that they cannot both be closed at the sametime and the connections are such that the closing of the first switchsets in operation a timing device which after the lapse of apredetermined interval energizes the second switch and deenergizes thefirst switch.

In the accompanying drawings illustrating one embodiment of myinvention, Figure 1 is a front elevation of a. switch embodying myimprovements; Fig. 2 is a side view of the same; Fig. 3 is a detailedview of the switch mechanism; Fig. 4 is a sectional view of the same;and Fig. 5 is a diagram showing the circuit connections.

Referring to Figs. 1 and 5, it will be seen that I have provided twoelectromagnetically operated switches or contactors A and B. Contactor Ais for making the starting connections and contactor B for making therunning connections. C represents an autotransformer or compensatorwhich is connected in circuit between the line and the motor by theclosing of the switch A. M represents the electric motor to becontrolled, which I have shown as a three-phase motor of the squirrelcage type. This switch A is first closed, thereby connecting the.

motor to the line through the starting compensator and after apredetermined interval the switch B is closed and switch A opened,thereby connecting the motor directly to the line.

Referring now to Fig. 1, it will be seen that contactor A comprises anoperating winding 10 having a pivoted armature 11 which operates a shaft12 upon which are mounted contact fingers 131 1151617, cooperating withstationary contacts, 18, 19, 20, 21 and 22. This contactor is normallyin open position but when the winding 10 is energized, th shaft 12 isturned on its axis and moves the stationary contacts into engagementwith the fixed contacts. The contactor B is similar to contactor A,being provided with an operating winding 23 cooperating with an armature24 which turns a shaft25 upon which are moimted the three contactfingers 26, 27, and 28 cooperating with stationary contacts 29, 30 and31. The two contactors A and B are mechanically interlocked by aninterlock bar 32 which prevents the two contactors from closed at thesame time. This is a well-known arrangement and requires no furtherdescription.

Cooperating with the contactor A is a. timing device comprising an arm33 which is secured to the shaft 12 so as to be turned when thecontactor is closed. A member I to the rod and operating in a cylinder38. The piston moves freely in the cylinder from left to right as shownin Fig. 3 but is retarded in its movement from right to left. When thecontactor A closes, the spring 35 will be compressed thereby giving thelower end of the member 34 a tendency to move to the left, whichmovement is retarded by the dash pot. In moving in the oppositedirection, however, the dash pot has no substantial retarding effect.

A switch arm 39 pivoted at 40 on the shaft 25 has its free end engagedby the member 34 as the latter moves to the left (Fig. 3) so as tobridge the two contacts 41 and 42, that is, the switch arm is moved fromthe position in which it is wholly in engagement with the contact 41 tothe position where it bridges the contacts 41 and 42 and finally engagesonly the contact 42. Contact 41 is connected with thewindihg 10 ofcontactor A and contact 42 is connected with the winding 23 of contactorB, so that when the switch arm is in engagement with the 0011- tact 41,contactor A will be energized, and when it is in connection with contact42, contactor B will be energized. The two contactor-s A and B are,therefore, energized at the same time, but as before pointed out theycannot both close because of the mechanical interlock. The switch arm 39is moved in the opposite direction; viz., to the right by the arm 33,which is secured to the shaft of contactor A. As shown in Fig. 3 the arm33 and the member 34 are shaped at their lower ends to form a slot oropening 43 into which a pin 44 on the end of the switch arm 39 fits. Theswitch arm is therefore moved to the left slowly after the contactor Acloses and is moved to the right quickly by the arm 33 when thecontactor A opens. The contacts 41 and 42 which are engaged by theswitch arm 39 are mounted on a plate 45 of insulating material securedto a metallic plate 46 which in turn is secured to the shaft 25 ofcontactor B. When the contactor B is open the plate 45 occupies theposition shown in full lines in Fig. 3 and when the contactor is closedthe plate is turned to the position shown in dotted lines.

The operation of the switch mechanism is, therefore as follows: Whenthecontactor A closes the arm 33 is rotated (in a clockwise direction inFig. 3) so as to compress the spring 35, thereby causingthe member 34 tomove slowly in response to the sprin pressure under the retardation ofthe dash pot. The switch arm 39 is carried forward by the member 34until it engages contact 42 while it is still in engagement withcon- Itact 41. The windings of both switches are now energized, but because ofthe mechanical interlock they cannot both close. The switch A beingclosed, therefore, prevents switch B from closing. When the switch armmoves forward the engagement is broken with contact 41 therebydeenergizing the winding of contactor A and permitting it to open. Assoon as contactor A is de'e'nergized, contactor B which is alreadyenergized, closes, while contactor A opens. The opening of contactor Acarries the switch arm 39 back to its initial position and the closingof contactor B moves the plate 45 carrying contacts 41 and 42 back inthe same direction. The result is that the switch arm and the contactare moved back together, the switch arm being in engagement with contact42. Contactor B therefore remains closed, thereby maintaining therunning connection. When contactor B opens for any reason the plate 45will return to its initial position shown in full lines in Fig. 3.

The arrangement of circuits and mode of operation are as follows:Referring to Fig. 5, 47 indicates a manually operated, normally openedswitch or push button for energizing contactor A, and 48 is a normallyclosed switch or push button for opening the contactors. \Vhen the pushbutton 47 is, therefore, pressed for an instant the operating winding 10of contactor A is energized, the circuit being'as follows: from line bof the three-phase supply circuit, through the contacts 49 of theoverload relays 50, to the switch arm 39, thence to contact 41, wire 51,through winding 10, switch 47, stop button 48, and thence back to main 0on wire 52. This causes the contactor A to close thereby connecting themotor to the line through the autotransformer C. These connections areobvious and need not be traced. \Vhen V the contactor A closes, it movesthe arm 33 on its pivot and compresses the spring 35. Pressure of thespring 35 upon the member 34 moves the member slowly due to theretardation of the dash pot. The switch arm 39 therefore moves slowlyuntil it engages the contact 42, whereupon the winding 23 of contactor Bis energized, the circuit being from line 6 through the contacts of theoverload relays to switch arm 39,- contact 42, winding 23, thencethrough the stop button 48 and back to line 0 by wire 52. The windingsof contactors A and B are now both energized but contactor B cannotclose because of the mechanical interlock which prevents it from closingwhile contactor A is closed. A further movement of the switch arm 39,however, disengages it from contact 41 thereby denergizing winding 10 ofcontactor A. This now permits contactor B to close and contactor A toopen, contactor A,

ingthe contacts 41 and 42 to the left. Since the opening of contactor Awill cause the switch arm 39 to also move to the left the switch arm andthe plate move together, the switch arm being in engagement with contact42-, thereby maintaining the circuit of winding 23 of contactor B. Theparts will, therefore, remain in this position; namely, with thecontactor B closed and A opened. Contactor B is opened either by theoperation of the overload relays, by failure of voltage, or by theoperation of the stop button 48. Then the contactor B is opened due toany of these causes the motor, of course, is disconnected from the lineand the plate 45 is returned to the right (Fig. 5), so that the partswill assume the position shown in Fig. 5. In order to start again thepush button 47 must be pressed and the operation above describedrepeated. It should be noted that when the contactor A closes; the

- push button 47 which caused the closing of the contactor is shortoircuited by the contact finger 53 which operates with the contactor A.The push button 47 need be pressed only for an instant, therefore, inorder to start the operation, and unless the operation is interrupted bythe operation of the stop button 48, it will continue and bring themotor up to running speed.

It will be seen, therefore, that I have provided a simpleand eifectivedevice which will automatically make the starting and runningconnections successively upon the actuation of a push button, theoperations all being positive and certain While I have described myinvention as embodied. in concrete form and as operating in a specificmanner inaccordance with the provisions of the patent statutes, itshould be understood that I do not limit my invention thereto as variousmodifications thereof will suggest themselves to those skilled in theart without departing from the spirit of my invention the scope of whichis set forth in the annexed claims.

What I. claim as new and desire to secure by Letters Patent of theUnited States, is

,1. A controller for electric motors comprising an electromagneticallyoperated starting switch and means for energizing the same, anelectromagnetically operated running switch, means set in operation bythe closing of the starting switch and retarded in its action for adefinite interval of time, and connections whereby the said meansdenergizes the starting switch and causes this switch to open andimmediately thereafter energize the running switch to cause it to close.

2. A controller for electric motors comprising two electromagneticallyoperated switches, one for starting and one for running, a manuallyoperated switch for controlling the starting switch, a time elementdevice for controlling the circuits of said electromagnetic switches andnormally in a position to energize the starting switch,

means for setting the time element device in operation upon the closingof the starting switch, and connections whereby the time element devicede'einergizes the starting switch and immediately thereafter energizesthe running switch.

3. A controller for electric motors comprising two electromagneticallyoperated switches, one for starting and one for running, a time elementdevice for controlling the circuits of said electromagnetic switches andmeans for setting the time element device in operation upon the closingof the starting switch to energize the running switch and deenergize thestarting switch, said time element device being returned upon theclosing of the running switch.

4. A. controller for electric motors comprising two electromagneticallyoperated switches, one for starting and one for running, a springactuated time element device retarded in its action for controlling thecircuits of said electromagnetic switches, connections whereby saiddevice in its movement .energizes the running switch and deenerg'izesthe starting switch and means for placing the spring under strain uponthe closing of the starting switch.

5. A controller for electric motors com prising two electromagneticallyoperated switches, one for starting and one for running, a springactuated time element device retarded in its action for controlling thecircuits of said electromagnetic switches, connections whereby saiddevice in its movement energizes the running switch and deenergizes thestarting switch, means for placing the spring under strain upon theclosing of the star-ting switch and means for returning the time elementdevice upon the closing of the running switch without deenergizing thelatter.

6. A controller for electricmotors comprising two electromagneticallyoperated I switches, one for starting and one for running, a springactuated time element switch member retardedin its action and set inoperation by the closing of the starting switch, and a member actuatedby the running switch and contacting with the said switch member tocontrol the circuits of said electromagnetic switches.

In witness whereof I have hereunto set my hand this 6th day of January,1919.

PAUL H. ZIMMER.

